It is known to use a laser beam for cutting an acoustic wave device. For example, there is known a method for cutting a bonded substrate in which a base substrate and a lid substrate are bonded. In the method, a nick is formed by irradiating the lid substrate with a laser beam, and then the bonded substrate is pushed from a base substrate side, thereby cutting the bonded substrate (e.g. Japanese Patent Application Publication No. 2012-209617). For example, there is known a method for cutting a bonded substrate in which a supporting substrate and a piezoelectric substrate are bonded. In the method, a reforming region is formed by irradiating the supporting substrate with a laser beam, and then the bonded substrate is cut at the reforming region (e.g. Japanese Patent Application Publication No. 2014-22966).
As described in Japanese Patent Application Publication No. 2014-22966, the reforming region is formed by irradiating the supporting substrate with the laser beam, and then the bonded substrate is cut at the reforming region. Thereby, it is possible to suppress the occurrence of chipping and cracks. However, there is still room for improvement in the cutting method of the bonded substrate.